Compressor



R. c. HILTON; COMPRESSOR.

APPLICATION FILED 'DEC. 10, 1919.

Patented Feb. 21, 1921 2 SHEETS-SHEET 1.

- INVENTOR I Roland Cl-hon ATTORIVHS RFC. HILTON.

COMPRESSOR. APPLICATIQN FILED DEC.10, 1 91s.

Z 2 9 m3 Z @m d2 m m m w 4 Z 5 2 Mm INVENTOB Roland C. HHfon BY MWpW ATTORNEYS ATENT OFFICE.

. ROLAND o. HILTON, F TROY, NEW YORK, ASSIGNOR T0 Renoir-Huron, me, or

TROY, NEW YORK, A CORPORATION OF YORK.

' COMPRESSOR.

Application filed December 10, 1919. Serial No. 343,869.

v To all whom it may concern:

Be it known that I, ROLAND C. HILTON, a citizen of the United States, andaresident of Troy, county of Rensselaer, State of New York, have invented certain new anduseful Improvements in Compressors, of which the following is a specification.

This invention relates to compressors for air or other gases, and with regard to the more specific features thereof to the type of air compressor commonly connected to or mounted upon automobile engines and 1ntended to be driven therefromfor filling the pneumatic tires with compressed air. Ap-

paratus of this type is commonly designated by the name of tire pump.

As conducive to a clear understanding of the specific purpose of the invention it may be pointed out that lubricating oil has a deleterious effect on the inner tubes of pneumatic tires and that the entry of even a small quantity of such oil may materially shorten the life of such inner tubes. Accordingly it is an object of this invention to provide a tire pump which shall be substantially proof against the entry of lubricating oil into the tire and the action of which shall be eificient and smooth. The invention however has a broader application to compressors generally, and specifically to any relation in which it is desired to compress air or other gas in substantially pure form, free from foreign matter such as lubricating oil.

While the structure of this invention is more particularly applicable to the pumping of pneumatic tires, yet, owing to its special construction, whereby great economy of functioning is obtained, it is designed to be used generally in the arts wherever compressed air or other gas is used.

Where either compressed air or other gas is used in the arts it is highly desirable that the air or other gases should be supplied as free from impurities as possible and this is accomplished with the highest degree of efficiency and economy by the construction of my compressor as hereinafter described.

Other objects will be in part obvious, in part pointed out hereinafter.

To make clear my invention I have illus trated in the drawings a selected embodiment thereof which will now be described after which the novel features will he pointed out in the appended claims.

In the drawings Fig. 1 shows a vertical section of a compressor embodying my invention, the piston being shown at its lowermost positio i Fig. 2 is a section taken along the line 2-2 of Fig. 3. l

Fig. 3 is a section taken along the'line 9-3 of Fig. 1, the piston being shown inan intermediate position. i 1 F 1g. 4 is a view similar to Fig. 3, show.- 111 the piston in uppermost position."

The application is a continuation ofm co-pending application, Serial No. 275,369,

filed February 6th, 1919, asto all common sub ect matter. a Y The pumpshown comprises-a cylinder- 1 and a crankcase 2 with which the cylinder communicates, said crankcase having a crank shaft 3 therein which is provided with a crank pin 4: that is connected by the connecting rod 5 to the piston indicated generally at 6. The pump is preferably mounted upon an engine, a fragment'of which is indicated 1n dotted lines. A quantity of lubricating 011 0 lies in the crank case 2 and is necessarily thrown against surfaces of relatively eating systems generally.

The cylinder is formed with two portions of different diameter,.7 indicating the portion of larger diameter, and '8 the portion moving parts, in the manner of splash lubriof smaller diameter, said two portionsbein'g connected by an oblique or conical ledge 9. The piston is likewise provided with two portions 10 and 11 of difierent'diameter connected by an oblique or sloping shoulder 9 parallel to ledge 9, the portion'lO'of larger diameter operating in the cylinder portion 7 of larger diameter and the piston portion 11 of smaller diameter operating in the cylinder portion 8 of smaller diameter;

Both portions of the piston will preferably I be provided with suitable piston rings '30 to make a tight joint. The piston portion 10 of larger diameter thus divides the cylinder portion 7 into two "compression chambers, a first stage compression chamber 12 between the head of the cylinder'and the head of the piston and asecond stage compression chamber 13 annular in form, between the eylinder portion? and the pist'on portion 11. 4

The cylinder is preferably provided with an inlet valve 14 in its head, controlling the inlet port 15. The detailed construction of this inlet valve need notibe"described,jit

being simply no'tedthat this'valve is-urged 7 charge port 20, which port is in communication preferably with the lower end of the second stage compression chamber 13. The valve 19 has a stem 21, a' relatively strong coil compression spring 23 urging the valve against its seat 22. A by-pass is provided for conveying the compressed air past the valve stem to the tire when the valve is open.

I provide means for conveying air from the first stage compression chamber 12 to the annular or second stage compression chamber 13, this means preferably comprising a port 24 through a valve seat plug 25, preferably threaded into the piston, and normally closed by a valve 26, urged against its seat by coil compression spring 27.

The stroke of the piston is preferably such that at lower dead center an appreciable space 28is left between the lower end of the larger piston 7 and the ledge 9. To assure smooth operation a small space 29 is also left between the upper end of the piston and the head of the cylinder when the compressor is at upper dead center, as shown in Fig. 4.

The lower end of the piston with the piston rings 30 normally substantially closes the cylinder against the entry of lubricating oil from the crank case. If, however, during operation a suction were allowed to take place at a region intermediate the lower end of the piston and the discharge port, an appreciable amount-of lubricating oil might be i V sucked past the said piston rings and would find its way to the inner tube with the deleterious effect thereon above noted. By my construction as will appear in the detailed description of the operation below, such suction action is entirely avoided, so that the life of the tire will not be shortened by the presence of oil.

The operation proceeds as follows:

The compressor being operatively connected to the engine or to some other source of power by a suitable transmission (not shown) the rotation of the crank pin 1 brings about a reciprocation of the piston 6 and a consequent substantially continuous splash of the lubricant 0 in the bottom of'the crank Valve 1a to close.

sion chamber has its maximum volume and is filled with air under atmospheric pressure, and spring 17 accordingly causes the intake The charge of air thus taken into the compressorwill now be traced in its travel under compression to the tire.

Upon the upward stroke of the piston, the charge of air in the compression chamber 12 is compressed and shortly after the beginning of this upward stroke the pressure in said chamber sufiiciently exceeds that in the annular or second stage chamber 13 that the valve 26 in the piston is caused to open against the resistance of spring 27 and the compressed air in the first stage chamber is forced into the annular or second stage chamber 13, until the uppermost position of the piston shown in Fig. 4 is reached. In this position the first stage compression chamber has been substantially eliminated, the air having been forced therefrom into the annular or second stage compression chamber 13. The parts are preferably so designed that during this process approximately one half of the compression of the air has been efiected.

Upon the succeeding downward stroke of the piston a fresh charge of air is sucked into the first stage compression chamber in the manner above described. During this stroke, the air in the second stage chamber 13 is still further compressed and the strength of spring 28 of the discharge valve is preferably such that said valve will not be caused to open until the piston nears the lower end of its stroke. During the lowermost portion of the stroke accordingly the discharge valve is forced open, allowing the highly compressed air to pass into the tire or other receiver. When the piston reaches its lowermost position the valve 19 is closed by the spring 23 there being a small volume of air .under relatively high compression in what remains of the second stage compression chamber 13 as shown in Fig. 1. The air in this chamber is of course under a pressure slightly below that needed to cause an opening of the valve 19 against the strong valve spring 23.

As the piston now returns upon its upward stroke it compresses the charge of air thereabove in the manner alreadydescribed,

and the highly compressed air remaining in the second stage chamber 18 after closure of the valve 19, expands.

Thus, as the pressure in the annular compression chamber 13 is reduced on the up ward stroke, by expansion that of the succeeding charge in the first stage chamber 12 is simultaneously increased by compression, and the strength of the valve spring 27 controlling the valve 26 in the piston head is preferably such that the valve will open by the excess of pressure in. chamber 12, to equalize the pressures in the two chambers before the pressure in the annular chamber 1 0 13 has been reduced below that of the air in the crankcase 3. Preferably, however, valve 26 is caused to open at a time when the pressure in chamber 13 is still appreciably above atmospheric. It will be apparent that the oblique or conical arrangement of the ledge 9 and shoulder 9 affords a greater minimum volume of compression chamber 13, than if these elements were parallel to the piston head.

After the valve opens, and during the remainder of the upward stroke of the piston the pressure in the annular chamber continually rises from the minimum value, in the manner above noted. 7

By the operation above described it will be seen that the pressure in the annular compression chamber 13 is considerably above atmospheric while the piston valve 26 is open during the upward stroke, and is still higher throughout the downwardstroke of the piston. During the first part of the upward stroke of the piston as above pointed out, the pressure in the annular compression chamber reaches its lowest value and this lowest value as noted should be at least as high as the pressure in the crank case at all times. Therefore during the upward stroke of the piston the pressure in the annular chamber 13 is never less than the pressure in the crank case below the piston.

It will thus appear that no suction at any time occurs to" draw lubricating oil from the crank case 3 past the piston rings 11 into the discharge port and thence to the tire. By reason of the high compression persisting for the greatest portion of the cycle in the annular compression chamber '13 a pneumatic expulsion action is exercised upon any lubricating oil tending to enter said chamber from the crank-case.

My construction thus provides an air chamber or reservoir between a part of the piston and the side wall of the cylinder in which the air is always maintained under a pressure to prevent the passage of free lubricant.

Practical tests of the pump above described and shown have demonstrated that no lubricating oil will pass the discharge valve 19. I/Vhen a piece of white blotting paper by way of experiment was placed in front of the discharge port during operation of the pump, it was found that this paper remained clean and dry.

The piston rings 11 in the larger part of the cylinder may, if desired, be of graphite or other lubricating composition. It has been found upon careful .disassembly of the pump immediately after an extended operation that the inner wall of the larger portion of the cylinder has a fine oily film thereon.

I do not know how this lubrication takes place, but I have advanced the following explanation to account for this operation,

which explanation it is to be understood is merely tentatively advanced and by which I do not wish to be bound. 1

At the beginning of the upward stroke of lubricant being in quantities too minute to form drops, but constituting a very thin film adhering by molecular attraction to the wall 7 of the cylinder. In other words this small quantity of oil is neverin a free condition such as to be carried away by air under compression.

' It is thus seen that I have provided a tire pump or compressor which is properly lubricated for smooth and'eflicient action and which nevertheless prevents the entry of any lubricant into the pneumatic tire or the re ceiver. V Y Although I have shown my compressor as of the two-stage type, it is to be understood that theinvention is also applicable to single-stage compressors, and that modifications may be made within the scope of the appended claims, involving constructions in which the compression chamber that resists the entry of lubricating oil from the crankcase to the discharge port is arranged in other manners, either in direct communication with the discharge port or not. It is to be understood however that-I prefer the specific construction shown and described. It is also apparent that many of the features of this invention are applicable to pumps as well as to compressors.

It will thus be seen that there is herein described apparatus in which the several features ofthis invention are embodied, and which apparatus in its action attains the various objects of the invention and is well suited to meet the requirements ofpractical use.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departingfrom the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 1'

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a compressor, the combination with a reservoir for lubricant of a cylinder having a discharge port, a piston substantially closing said cylinder against the entry of lubricant from said reservoir, an air chamber between one part of said piston and said cylinder, said air chamber havingapo'rtion interposed between said lubricant reservoir and said port, and means for maintaining the pressure in said air chamber at all times at least as high as that of the air in said lubricant reservoir.

2. In an air compressor, the combination with a crank-case containing lubricant of a cylinder having a discharge port,,a piston substantially closing said cylinder against the entry of lubricant from said crankcase, an air chamber between said cylinder and said piston, said air chamber being located in the path of any lubricant tending to. pass from said crankcase tosaid port, and means for maintaining the pressure in said chamber at all times at least as high as that in said crankcase.

3. In a compressor, the combination with a crankcase containing lubricant, of a cylinder having a port, and a compression chamber communicating with the latter, said chamber having a portion thereof interposed in the path ofany lubricant tending to pass from said crankcase to said port, and means for maintaining a pressure in said compression chamber exceeding that in said crankcase throughout operation.

a. The combination in an air compressor of a crankcase, a cylinder'thereon having two portions of different diameter, a piston operating in said cylinder and also having two portions of different diameter, whereby an annular compression chamber is formed between axially aligned cylinder and'piston portions of difierent diameter, said annular chamber having an appreciable minimum volume, a discharge valve for said chamber and a pressure operated intake valve for maintaining the pressure in said chamber throughout operation in excess of that in said crank case,

5. The:- combination in a two-stage air compressor, of a crankcase containing lubricant, a cylinder thereon, a piston having two portions of different diameter, dividing said cylinder into a first-stage and a second-stage compression chamber, one of said piston portions substantially closing said cylinder against entry of lubricant, an air inlet to said first chamber, a compressed-air outlet from said second chamber, and means connecting said chambers to maintain a pressure in said second chamber exceeding that in said crankcase throughout operation.

6. The combination, in a two-stage compressor, of a crank case, a cylinder having two portions of different diameters, a piston having portions fitting one into each of said cylinder portions, whereby a first con'ipression chamber is formed between the end of said cylinder and that of said piston, and a second annular compression chamber is formed between the piston portion of smaller diameter and the cylinder portion of larger diameter, said annular chamber having an appreciable height at dead-center of the piston, an inlet valve in the end of said first compression chamber, a discharge valve in the side of said second compression chamber, and a pressure actuated valve in, said piston communicating between said chambers, said latter valves operating to maintain the pressure in the said annular chambers in excess of that in said crank case throughout the operation.

7. ln a pump, the combination with a pump casing comprising a crankcase anda cylinder connected thereto and opening di-. rectly thereinto, the outer end of the cylinder being of larger diameter than the inner end which opens into the crankcase, a shoulder connecting said cylinder portions, of a piston comprising a portion of larger diameter fitting the outer end of the cylinder and a portion of smaller diameter fitting the inner end thereof, and substantially closing said cylinder against theentry of lubricant from said crankcase, the stroke of saidpiston terminating at a distance from said shoulder, a crank shaft 'journaled in the crankcase, a connecting rod connecting the crank shaft and piston, an automatically operating inlet valve leading into the outer end of the cylinder portion of larger diameter, an automatically-operating discharge oil from working past the piston portion of.

smaller diameter.

8. In a compressor, the combination with a cylinder, a piston mounted for reciprocation therein, a gas chamber formed between the cylinder and the piston, a crank shaft, a crank connected to said piston and crank shaft, a crank chamber partially filled with lubricant in which chamber the said crank and crank shaft operate, and means for maintaining a pressure in the said gas chamber at all times during the upward stroke'of the piston in excess of the pressure in the crank chamber.

9. In a compressor, the combination with a cylinder, a piston therefor, an annular gas chamber-formed between the wall of the cylinder and parts of the piston, a crank shaft, a connecting rod between the said piston and crank shaft, a crank chamber partially filled with lubricant in which chamber the said crank and crank shaft operate, and means for maintaining a. pressure in the said annular gas chamber at all times during the upward stroke of the piston crank chamber partially filled with lubricant 10 which is in excess of the pressure of the in which chamber the said crank and crank crank chamber. shaft operate, and means for maintaining a 10. In a compressor, in combination With pressure in the said annular gas chamber at a cylinder, a piston mounted for reciprocaall times at least as high as that of the prestion therein, an annular gas chamber formed sure in the said crank chamber. 15

between the Walls of the cylinder and parts In testimony whereof, I have signed my of the piston, a crank shaft, a connecting name to this specification. rod between said piston and crank shaft, a ROLAND C. HILTON. 

